<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* div {
            height: 100vh;
            background: rgba(0, 0, 0, .7);
            color: #fff;
            line-height: 100vh;
            text-align: center;
            font-size: 20vh;
        }

        .a-img1 {
            background-image: url(https://images.pexels.com/photos/1097491/pexels-photo-1097491.jpeg);
            background-attachment: fixed;
            background-size: cover;
            background-position: center center;
        }

        .a-img2 {
            background-image: url(https://images.pexels.com/photos/2437299/pexels-photo-2437299.jpeg);
            background-attachment: fixed;
            background-size: cover;
            background-position: center center;
        }

        .a-img3 {
            background-image: url(https://images.pexels.com/photos/1005417/pexels-photo-1005417.jpeg);
            background-attachment: fixed;
            background-size: cover;
            background-position: center center;
        } */



        /* html {
            overflow: hidden;
            height: 100%
        }

        body {
            perspective: 1px;
            transform-style: preserve-3d;
            height: 100%;
            overflow-y: scroll;
            overflow-x: hidden;
        }

        #app {
            width: 100vw;
            height: 200vh;
            background: skyblue;
            padding-top: 100px;
        }

        .one {
            width: 500px;
            height: 200px;
            background: #409eff;
            transform: translateZ(0px);
            margin-bottom: 50px;
        }

        .two {
            width: 500px;
            height: 200px;
            background: #67c23a;
            transform: translateZ(-1px);
            margin-bottom: 150px;
        }

        .three {
            width: 500px;
            height: 200px;
            background: #e6a23c;
            transform: translateZ(-2px);
            margin-bottom: 150px;
        } */
        .border {
            width: 0;
            height: 0;
            border-top: 50px red solid;
            border-right: 50px transparent solid;
            position: relative;
            
        }
    </style>
</head>

<body>

    <div class="border"></div>
    <!-- <div class="a-text">1</div>
    <div class="a-img1">2</div>
    <div class="a-text">3</div>
    <div class="a-img2">4</div>
    <div class="a-text">5</div>
    <div class="a-img3">6</div>
    <div class="a-text">7</div> -->

    <!-- <div id="app">
        <div class="one">one</div>
        <div class="two">two</div>
        <div class="three">three</div>
    </div> -->
</body>

</html>